Therapeutic treatments, such as protein or enzyme replacement therapies, often result in undesired immune responses to the particular therapeutic. In such cases, cells of the immune system recognize the therapeutic as foreign and attempt to destroy it, just as they attempt to destroy infecting organisms such as bacteria and viruses. Such undesired immune responses may be reduced through the use of immunosuppressant drugs. Conventional immunosuppressant drugs, however, are broad-acting. Additionally, in order to maintain immunosuppression, immunosuppressant drug therapy is generally a life-long proposition. Unfortunately, the use of broad-acting immunosuppressants are associated with a risk of severe side effects, such as tumors, infections, nephrotoxicity and metabolic disorders. Accordingly, new immunosuppressant therapies would be beneficial.